I can't find the answer for this question anywhere on the internet. My friend and I made butterfly pea jelly with gelatin and we used the same recipe. Mine came out fine with blue color of butterfly pea flowers but my friend's changed its color to dark purple after adding gelatin.
My friend lives in Asia and me in Europe, so I think our source of ingredients (gelatin, water, flowers) is different. Plus, our method is slightly different. My friend heated the tea to melt gelatin while I stired gelatin over hot water to melt it and then mixed it up with the tea.
My friend is pretty sure it was because of gelatin because she didn't have this problem when trying with agar agar. Although I know butterfly pea tea is very sensitive to pH, I just can't find a good explanation for this. Is it really because of gelatin?